Technical Field
The present invention relates to an antenna which detects an arrival angle of a radio wave (reflected wave) on the basis of a phase difference between radio waves received by two antenna elements.
Background Art
In recent years, an on-vehicle sensing device with a millimeter-wave radar has been put into practical use. In this device, a radio wave is transmitted from a transmitting antenna mounted on an own vehicle, a reflected wave of the radio wave from another vehicle is received, and the distance to the other vehicle, the relative speed relative to the other vehicle, and the azimuth of the other vehicle are measured on the basis of the reflected wave. Such a sensing device desirably has a wide-angle detection area in order to be able to detect the other vehicle over a wide range.
In order to measure the azimuth of the other vehicle, it is simply necessary to detect an arrival angle of the reflected wave, and as its detection method, a monopulse method based on a phase difference between radio waves received by two antenna elements (a phase monopulse method) is known. A receiving antenna for the monopulse method includes, for example, a plurality of antenna elements as shown in PATENT LITERATURE 1, and each antenna element includes a feeder line extending from a converter and a plurality of radiating elements which are fed with power from the feeder line.